Specifying a WGS84 reference is subject to a lot of misinterpretation.

There are the following ways to specify a global GPS location

There is Degrees Decimal Notation.

DDD.DDDD N DDD.DDDD W
DDD.DDDD N DDD.DDDD E
DDD.DDDD S DDD.DDDD W
DDD.DDDD S DDD.DDDD E

There is Degrees Minutes Decimal Notation.

DDD,MM.MM N DDD,MM.MM W
DDD,MM.MM N DDD,MM.MM E
DDD,MM.MM S DDD,MM.MM W
DDD,MM.MM S DDD,MM.MM E

There is Degrees, Minutes, Seconds Notation.

DDD,MM,SS N DDD,MM,SS W
DDD,MM,SS N DDD,MM,SS E
DDD,MM,SS S DDD,MM,SS W
DDD,MM,SS S DDD,MM,SS E

There are 12 different formats each giving a different location but using the same numeric data

e.g.

45.6763 N 76.6783 W
45,67.63 N 76,67.83 E
45,67,63 N 76,67,83 W
45,67.63 N 76,67.83 W
45,67,63 S 76,67,83 W
45.6763 N 76.6783 E

Are at completely different locations.

This is why in the UK we mostly use Grid Square Referencing OSGB36, as it doesn't lead to confusion.

We have the same issues here in CA. Our searchers us UTM grid coordinates, but pilots use LAT/LON. Having a communications van
to help catch errors is very helpful.

Yes, but the original message specified both of the first two formats you state. Either one is clear, but to use both is conflicting.

I suppose in the UK you can ignore 'S', as it is entirely in the Northern Hemisphere, but you have to get E and W right thanks to that tricky Greenwich Meridian. In the US, GPS positions will always be N and W.

A

Good point. But is always good practice to specify whether your location is either east or west of the Greenwich Meridian an North or South of the equator.

There have been occasions where the UK HM coast guard have recieved emergency rescue calls south of the equator and east of the Greenwich Meridian.

When a using a GPS to call in a emergency location, specifing the coordinate or geodetic system is good practice also.

So, martinfocazio can you please clarify?

Hi martinfocazio,

If using Decimal Degrees notation. i.e. DDD.DDD N DDD.DDD W is the one being specified by the helo pilots I would use the following or something similar for the dispatch sentence format. As most GPS equipment can be setup to display 2 geoedetic coordinate systems i.e. a secondary coordinate system in addition to WGS84 Decimal Degrees. I would also ensure that the second coordinate system is outputing UTM coordinates for all the GPS equipment in use.


To notify dispatch of coordinates for an LZ, tell the dispatcher:

"We are setting up an LZ at (name of LZ)"
"DATUM is WGS84. Decimal Degrees GPS coordinates for LZ is as follows"
"FOUR ZERO DECIMAL FIVE-FIVE-NINER NORTH"
"SEVEN FIVE DECIMAL ONE-TWO-TWO WEST"

OK! I sent a copy of your message to them and they agreed, so there we are.

Martin,
Great call getting the actual stakeholders involved. It can really be enlightening to see the world from their viewpoint.

While I use GPS, even I learned something from the various postings in response to your initial post.